5.
Appendix A: Reference Circuit
5.1
WFI32-IoT Board Schematics
Figure 5-1. Power Distribution Switch for PKOB4
GND
10uF
25V
0603
C102
GND
GND
GND
GND
GND
GND
MIC2042
VBIAS
7
VIN
8
VIN
12
EN
2
/FAULT
3
SLEW
9
ILIM
6
VOUT
10
VOUT
11
VOUT
14
PGREF
13
PWRGD
1
UVLOIN
4
GND
5
U100
24.3k
0402
1%
R106
GND
3V3_PKOB
3V3_PKOB
0.1uF
10V
0402
C101
0.1uF
10V
0402
C104
10k
0402
5%
R101
10k
0402
5%
R107
10k
0402
5%
R102
442k
0402
1%
R104
GND
95.3k
0402
1%
R105
5.62k
0402
1%
R109
5V0
i
Power Class
270R
0402
1%
R110
5V0_USBGOOD
5V0_nUSBFLT
0.1uF
10V
0402
C100
22uF
16V
0805
C103
VBUS
10000pF
50V
0402
C105
1
TP103
3ms slew rate
1.5A output current, R83=CLF/ILIM=395/1.5=263.3ohms (22%
tolerance)
4.4V power good threshold,
VOUT(GOOD)=0.23*(1+R104/R110)=0.23*(1+442k/24.3k)=4.41
V
4.1V undervoltage in shutdown threshold,
VUVTH=0.23*(1+95.3k/5.62k)=4.13V
Figure 5-2. Li-Po Battery Connector/Charger
10uF
25V
0603
C106
GND
4.7uF
16V
0603
C108
RED
D100
GND
5V0
GND
5V0
GND
GND
4.7uF
16V
0603
C107
GND
VBAT_OUT
0R
0402
R111
0R
0402
DNP
R117
10k
0402
5%
R118
100k
0402
5%
R119
10k
0402
5%
R115
1k
0402
5%
R112
GREEN
D101
1k
0402
5%
R113
1
2
HDR-2 Male 1x2
J101
0R
0402
R120
0R
0402
R127
5V0
VBAT_OUT
VBAT
BLUE
D102
4.99k
0402
1%
R114
1
2
4
5
10
11
12
13
14
15
16
17
18
19
20
21
1
TP102
1
TP104
SEL Pin Low: From USB Port, input
current limit governed by USB specs,
PROG2= High,ILIMITUSB=500mA
SEL Pin High: ILIMITAC = 1.65A
PROG1 = 1000V/IREG=
1000/100m=10k, IREG = 100mA
PROG3=1000V/ITERMINATION=1000
V/10mA= 100k
By default, SEL Pin = Low
MCP73871
OUT
VPCC
SEL
3
PROG2
THERM
PG
6
STAT2
7
STAT1/LBO
8
TE
9
VSS
VSS
PROG3
PROG1
VBAT
VBAT
VBAT_SENSE
CE
IN
IN
OUT
EP
U101
EV36W50A
Appendix A: Reference Circuit
©
2022 Microchip Technology Inc.
and its subsidiaries
User Guide
DS50003262A-page 17
